The present invention relates to a new and improved construction of a positioning or adjustment device for an air valve or air flap member arranged in the charging air line or conduit of a diesel engine, particularly a diesel engine charged by a pressure wave-charging device.
In its more particular aspects the positioning device of the present development is of the type wherein a shutoff valve is incorporated into the flow path between an impingement line branching-off of the pressure oil line of the diesel engine and an oil return flow line. The impingement line or conduit is connected with an impingement chamber for a positioning or adjustment piston actuating the air valve or flap member, this positioning piston, in turn, being loaded by a continuously effective force. The shutoff valve can be activated by a control piston loaded by the pressure in the charging air line against the force of a spring, in order to impinge with pressurized oil the positioning piston in the opening direction of the air valve.
A positioning device of the previously mentioned type is already known to the art from German patent publication No. 2,631,257, published Jan. 26, 1978, wherein the shutoff valve is actuated in the opening direction by a control piston loaded in such switching direction by the pressure prevailing in the charging air line against the force of a spring. Only in the absence of any oil pressure is the shutoff valve closed, whereby then this shutoff valve only can be closed in the rest position of the positioning piston, where the air valve is closed, in the absence of oil pressure.
With such construction of positioning or adjustment device there is ensured that the air valve or flap, upon starting the engine, remains closed, and only upon exceeding for the first time the idling rotational speed following the starting operation, does this valve remain open during the entire running time of the engine, and also during renewed engine idling, until the engine is again turned-off.